Percentage Calculator

A percentage is a number expressed as a fraction of 100. The symbol % means 'per hundred', so 25% literally means 25 out of every 100, or 0.25 as a decimal. Percentages are used to compare proportions, describe changes (like discounts or interest rates), and express probabilities in a way that is easy to understand.

To calculate X% of a number Y, multiply Y by X then divide by 100, or equivalently multiply Y by (X/100). For example, 20% of 150 is (150 × 20) ÷ 100 = 30. Our calculator does this instantly so you don't need to do the math by hand.

Percentage change = ((new value − old value) ÷ old value) × 100. If a value went from 80 to 100, the percentage increase is ((100 − 80) ÷ 80) × 100 = 25%. A negative result indicates a decrease. This formula is used for price changes, growth rates, performance comparisons, and statistics.

Divide the part by the whole, then multiply by 100. For example, if you scored 42 out of 60 on a test, your percentage is (42 ÷ 60) × 100 = 70%. This 'X is what percent of Y' calculation is useful for grades, completion rates, and any ratio you want to express as a percentage.

Divide the numerator by the denominator, then multiply by 100. For example, 3/4 becomes (3 ÷ 4) × 100 = 75%. To go the other way, divide the percentage by 100 and simplify the resulting fraction. 60% = 60/100 = 3/5.

A percentage point is the absolute difference between two percentages, while percent change is the relative difference. If interest rates go from 4% to 5%, that's a 1 percentage point increase but a 25% relative increase. This distinction matters in finance, polling, and statistics.